1. Field of the Invention
This invention pertains to the field of bearings. More particularly, this invention pertains to the field of bearing blocks and fixtures that contain a set of split bearings to support a rotatable shaft or other element such as a ball in a ball and socket joint.
2. Description of the Prior Art
More and more articles are being made from roll goods; heavy cardboard boxes are being replaced with plastic bags; automobile paint finishes are being replaced with adhesive-coated plastic films; and newspaper photogravure is being replaced with high-speed photographed plastic film. In virtually all of these transitions there is involved the use of sheet goods wrapped or supported on a shaft, where the shaft is temporarily mounted horizontally and allowed to rotate to either unwind or windup a film, carrier or other type of thin material.
While in some of these operations it is sufficient to merely support the horizontal shaft temporarily in a rough saddle, in many, if not most present-day computer-controlled factory methods, the rotation of the shaft is precisely indexed to other operations and requires that the shaft be not only carefully supported in lubricated bearings but housed in a bearing block capable of quick and accurate opening and closing to permit rapid interchange of shafts. The traditional V-shaped open brass or bronze bearing saddle is coming to the end of its useful life.
Bearing blocks are not new; two general types prevail in industry today. The two-piece precision bearing block includes a base, mounted to a support surface, containing the bottom half of a precision ground bronze or other metal bearing and a top or cover that fits down on top of the base, containing the top half of the bearing where a bolt or other fastener is dropped through vertically aligned holes on either side of the bearing to clamp the shaft therein. Lines carrying lubricant to the bearing are connected to the top and bottom bearing halves. To replace the shaft, the bolts are removed, the top bearing half lifted from the shaft, the shaft interchanged, and the operation reversed. While this bearing block provides firm, steady shaft support it is considered too cumbersome and time-consuming for many high speed operations.
A one-piece bearing block (unitary assembly as opposed to two separate pieces) has been used where down-time for shaft interchange is required to be minimized. This block has an elongated base, carrying the lower bearing at one end, and is hinged to an elongated top or cover at the other end, where the cover carries the upper bearing for engagement with the lower bearing to hold the shaft therebetween. The base and top are held together by a bolt, pivotally mounted on the end of the base opposite the hinge and outboard of the bearing, that engages a two-prong dog, extending from the end of the cover, by means of a cross-pin. Closing pressure is applied by twisting a retaining nut down the bolt to force the cross-pin against the dog and squeeze the shaft between the top and bottom bearings. Problems have been encountered in that the closing mechanism, being on the opposite side of the bearing from the hinge, tends to pinch the shaft in the bearing, especially where interchanged shafts vary in diameter, introducing unwanted friction (sticking) into the shaft-rotation operation causing heat, loss of lubricant, uneven bearing wear and a higher incident of bearing replacement. In addition, the alignment of the closing bolt, precise positioning of the cross-pin in the hold-down dog and the tensioning of the retaining nut requires a degree of manual dexterity often found lacking in the labor force.